1. Field of the Invention
The invention relates to a resist underlayer film-forming composition and a method for forming a pattern.
2. Discussion of the Background
A semiconductor device production process normally includes forming a resist film on a substrate using a resist composition that includes a photosensitive substance, exposing a given area of the resist film, removing the exposed area or the unexposed area of the resist film by development to form a resist pattern, and dry-etching the substrate using the resist pattern as an etching mask.
Such a process utilizes ultraviolet rays (e.g., ArF excimer laser light) as exposure light used when exposing the resist film. Miniaturization of large-scale integration (LSI) circuits has been increasingly desired, and a resolution equal to or less than the exposure wavelength may be required. In this case, a shortage of the exposure process latitude (e.g., exposure latitude and depth of focus) occurs. It is effective to improve the resolution by reducing the thickness of the resist film in order to compensate for the shortage of the exposure process latitude. However, this makes it difficult to provide the resist film with a thickness necessary for etching the processing target film.
In order to deal with such a problem, a process that forms a resist underlayer film on a substrate, transfers a resist pattern to the resist underlayer film to form an underlayer film pattern, and transfers the resist pattern to the substrate using the underlayer film pattern as an etching mask (hereinafter may be referred to as “multilayer resist process”) has been studied. When using the multilayer resist process, it is desirable that the resist underlayer film be formed of a material that exhibits etching resistance. For example, a resist underlayer film-forming composition that contains a polymer that has a side-chain alkynyloxy group has been proposed as a material for forming the resist underlayer film (see Japanese Patent Application Publication (KOKAI) No. 2009-14816).
When subjecting a topological substrate to lithography during the multilayer resist process, it is necessary to planarize the topological substrate by filling depressions formed in the topological substrate. In this case, a resist underlayer film-forming composition may be applied to the topological substrate to form a resist underlayer film, and the resist underlayer film may be planarized. However, since the in-plane depression distribution has become non-uniform due to an increase in aspect ratio (i.e., the ratio of the width (line width) to the thickness of the underlayer film pattern), it has become difficult to achieve planarization while filling depressions. On the other hand, the resist underlayer film-forming composition is required to reduce generation of outgas when forming the resist underlayer film to suppress contamination of the production system.
Therefore, a resist underlayer film-forming composition that can form a resist underlayer film that exhibits excellent etching resistance, exhibits an excellent depression filling capability, and reduces generation of outgas when forming the resist underlayer film, has been desired.